Why do I get constant nosebleeds?

Why do I get nosebleeds randomly and sometimes black out halfway?

• in the middle of a season such as summer or winter, i barely get nosebleeds unless I get hit on the nose. In autumn or spring the nosebleeds happen very frequently. Sometimes after a nosebleed, I have this little black out that takes about 10 - 15 seconds. I can still stand, but I can't control anything. One time I even collapsed and the next thing I knew, I was laying on the ground. I had suspicion that this might be because of the changes in humidity as I live in Southern Manitoba Canada and humidity changes very much here. It is very dry in the winter and humid/moist in the summer. One time I had a hot/warm shower and I had a blackout, but this also happens when I work out (especially when I do push-ups). Please help, I don't know what is happening to me. Might it be a brain tumour or something?

• Answer:

  Mine does too, but its because i go outside to the sun, i have to wear hats because it starts bleeding.